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- Title
Persistent Eastward EEJ Enhancement During the Geomagnetic Storm Recovery Phases.
- Authors
Li, Qiaoling; Zhang, Ruilong; Liu, Libo; Kuai, Jiawei; Yang, Na; Zhong, Jiahao; Wan, Xin; Liu, Jing
- Abstract
Recent case studies disclosed that sometimes the dayside ionospheric equatorial electric field underwent persistent long‐duration (>4 hr) eastward enhancements during geomagnetic storm recovery phases, rather than anticipated decrease or reversal. However, it is still unknown the occurrence and morphology of the persistent enhancement as well as its impact on the low‐latitude ionospheric plasma distribution. For the first time, we examined the issue with superposed epoch analyses of equatorial electrojet (EEJ) and GNSS total electron content (TEC) responses in the American (49°W) and Indian (78°E) sectors. The occurrence rates of the persistent enhancement during storm recovery phases are more than 30%, with higher occurrence rates in second to fourth days of the recovery phase, equinoxes, and American sector. The corresponding averaged EEJ and TEC responses were disclosed and compared with those storm samples without the persistent enhancement. On the first day of recovery phase, the dayside equatorial ionosphere was dominated by the prevalent westward electric field and causative inhibited equatorial fountain. In contrast, after the first day, the dayside morphologies showed different patterns: (a) for the persistent cases, the large eastward EEJ and TEC enhancement indicated the enhanced eastward electric field at forenoon and causative intensified equatorial fountain. (b) For the storms without the persistent cases, the general westward EEJ and equatorial TEC enhancements were dominated. Our study indicates that dayside eastward enhancement is an important disturbed pattern of equatorial ionospheric electric field during the late recovery phases, and the enhancement generally causes the intensification of equatorial ionization anomaly. Plain Language Summary: During geomagnetic storm recovery phases, the dayside ionospheric equatorial electric field sometimes presented long‐duration (>4 hr) eastward enhancement for several days (simply called persistent eastward enhancement), which is not consistent with the general feature due to the neutral wind disturbance dynamo effects. How about the climatology and the impact to the plasma distribution of the unique enhancement? Using long‐term ground‐based equatorial electrojet (EEJ) and total electron content (TEC) observations, we showed that the persistent enhancement occurred often (rates reach up to 46%) and mostly happened in second to fourth days of the recovery phase, equinoxes, and American sector. Moreover, we found that the averaged responses of EEJ corresponding to the persistent enhancements generally displayed eastward enhancement before 15:00 LT, and the dayside averaged TEC indicated the enhanced equatorial ionization anomaly. Our study provided robust evidence that dayside eastward enhancement is an important disturbed pattern of equatorial ionospheric electric field during the late recovery phase, and the enhancement can strengthen the equatorial fountain effects and further influence the plasma distribution at low latitudes. Key Points: Superposed epoch analyses are applied to EEJ and TEC during the geomagnetic storm recovery phaseOccurrence rate of the persistent eastward EEJ enhancement is more than 30% and depends on longitude, season, and storm phasePrevalent westward electric field is not dominated after the first day of the recovery phase
- Subjects
MAGNETIC storms; EQUATORIAL electrojet; ELECTRIC fields; IONOSPHERIC plasma; IONOSPHERE
- Publication
Journal of Geophysical Research. Space Physics, 2022, Vol 127, Issue 5, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA030258